Scalar scattering amplitude in Gaussian wave-packet formalism

Abstract

We compute an $s$-channel $2\to 2$ scalar scattering $\varphi \varphi \to \Phi \to \varphi \varphi$ in the Gaussian wave-packet formalism at the tree-level. We find that wave-packet effects, including shifts of the pole and width of the propagator of $\Phi$, persist even when we do not take into account the time-boundary effect for $2\to 2$, proposed earlier. The result can be interpreted that a heavy scalar $1\to 2$ decay $\Phi \to \varphi \varphi$, taking into account the production of $\Phi$, does not exhibit the in-state time-boundary effect unless we further take into account in-boundary effects for the $2\to 2$ scattering. We also show various plane-wave limits.

31 pages, 1 figure, minor typo corrections, version to appear in PTEP